This invention relates to flexible hoses consisting of foamed layers protected by a nonfoamed or less-foamed outer cover and an inner tube. Prior technology teaching the coextrusion of multiple layers of foamed, plastic material to make flexible, lightweight hose is shown in U.S. Pat. No. 4,044,799 to Higbee et al, and in U.S. Pat. No. 3,547,162 to Schaerer et al. The foaming of the material also improves the economics because it reduces the density, using less material per unit length.
However, this hose is not without its disadvantages. It has been noted that a foamed hose cover is not as resistant to staining or abrasion. The porous nature of the cover makes it particularly susceptible to staining, making the hose look worn long before the end of its useful like.
It is known in the art that a thin nonfoamed layer may also be applied to the inside of the tube. With a nonporous, thin skin acting as a liner, it isn't necessary to be concerned with the porosity of the foamed layers from a permeability standpoint, because the skin insulates the foamed layers from the fluid by serving as a permeability barrier.